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CVE-2026-64045 (GCVE-0-2026-64045)

Vulnerability from cvelistv5 – Published: 2026-07-19 15:39 – Updated: 2026-08-05 12:38
VLAI
Title
ovpn: tcp - use cached peer pointer in ovpn_tcp_close()
Summary
In the Linux kernel, the following vulnerability has been resolved: ovpn: tcp - use cached peer pointer in ovpn_tcp_close() ovpn_tcp_close() loads the ovpn_socket via rcu_dereference_sk_user_data() under rcu_read_lock(), takes a reference on sock->peer, caches the peer pointer in a local, and drops the read lock. It then passes sock->peer (rather than the cached local) to ovpn_peer_del(), re-dereferencing the ovpn_socket after the RCU read section has ended. Unlike ovpn_tcp_sendmsg(), which uses the same "load under RCU, use after unlock" pattern but is protected by lock_sock() held across the function, ovpn_tcp_close() runs without the socket lock: inet_release() invokes sk_prot->close() without taking lock_sock first. ovpn_socket_release() can therefore complete its kref_put -> detach -> synchronize_rcu -> kfree(sock) sequence concurrently, in the window after ovpn_tcp_close() drops rcu_read_lock() but before it dereferences sock->peer. The synchronize_rcu() in ovpn_socket_release() protects readers that use the dereferenced pointer inside the RCU read section, not those that escape the pointer to a local and use it afterwards. A reproducer follows the pattern of commit 94560267d6c4 ("ovpn: tcp - don't deref NULL sk_socket member after tcp_close()"): trigger a peer removal (keepalive expiration or netlink OVPN_CMD_DEL_PEER) at the same moment userspace closes the TCP fd. That commit fixed the detach-side of the same race window; this one fixes the close-side at a different victim. Tighten the entry block to read sock->peer exactly once into the cached peer local, and route all subsequent uses (the hold check, the ovpn_peer_del() call, and the prot->close() invocation) through that local. sock->peer is only ever written once in ovpn_socket_new() under lock_sock(), before rcu_assign_sk_user_data() publishes the ovpn_socket, and is never reassigned afterwards - but the previous multi-read pattern made that invariant implicit rather than explicit. The same multi-read shape exists in ovpn_tcp_recvmsg(), ovpn_tcp_sendmsg(), ovpn_tcp_data_ready() and ovpn_tcp_write_space(); those will be cleaned up via a dedicated helper in a follow-up net-next series.
Severity
8.4 (High)
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 11851cbd60ea1e5abbd97619d69845ead99303d6 , < e5460eb7238c19d651a9b22b2378b587033a4095 (git)
Affected: 11851cbd60ea1e5abbd97619d69845ead99303d6 , < d3ef441907fca7c340979e577a3db3bb634bf166 (git)
Affected: 11851cbd60ea1e5abbd97619d69845ead99303d6 , < 775d8d7ad02aa345e1588424a6a8b9ae49fb9012 (git)
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Linux Linux Affected: 6.16
Unaffected: 0 , < 6.16 (semver)
Unaffected: 6.18.34 , ≤ 6.18.* (semver)
Unaffected: 7.0.11 , ≤ 7.0.* (semver)
Unaffected: 7.1 , ≤ * (original_commit_for_fix)
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{
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          "product": "Linux",
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\novpn: tcp - use cached peer pointer in ovpn_tcp_close()\n\novpn_tcp_close() loads the ovpn_socket via rcu_dereference_sk_user_data()\nunder rcu_read_lock(), takes a reference on sock-\u003epeer, caches the peer\npointer in a local, and drops the read lock. It then passes sock-\u003epeer\n(rather than the cached local) to ovpn_peer_del(), re-dereferencing the\novpn_socket after the RCU read section has ended.\n\nUnlike ovpn_tcp_sendmsg(), which uses the same \"load under RCU, use\nafter unlock\" pattern but is protected by lock_sock() held across the\nfunction, ovpn_tcp_close() runs without the socket lock: inet_release()\ninvokes sk_prot-\u003eclose() without taking lock_sock first.\n\novpn_socket_release() can therefore complete its kref_put -\u003e detach -\u003e\nsynchronize_rcu -\u003e kfree(sock) sequence concurrently, in the window\nafter ovpn_tcp_close() drops rcu_read_lock() but before it dereferences\nsock-\u003epeer. The synchronize_rcu() in ovpn_socket_release() protects\nreaders that use the dereferenced pointer inside the RCU read section,\nnot those that escape the pointer to a local and use it afterwards.\n\nA reproducer follows the pattern of commit 94560267d6c4 (\"ovpn: tcp -\ndon\u0027t deref NULL sk_socket member after tcp_close()\"): trigger a peer\nremoval (keepalive expiration or netlink OVPN_CMD_DEL_PEER) at the same\nmoment userspace closes the TCP fd. That commit fixed the detach-side\nof the same race window; this one fixes the close-side at a different\nvictim.\n\nTighten the entry block to read sock-\u003epeer exactly once into the cached\npeer local, and route all subsequent uses (the hold check, the\novpn_peer_del() call, and the prot-\u003eclose() invocation) through that\nlocal. sock-\u003epeer is only ever written once in ovpn_socket_new() under\nlock_sock(), before rcu_assign_sk_user_data() publishes the ovpn_socket,\nand is never reassigned afterwards - but the previous multi-read pattern\nmade that invariant implicit rather than explicit. The same multi-read\nshape exists in ovpn_tcp_recvmsg(), ovpn_tcp_sendmsg(),\novpn_tcp_data_ready() and ovpn_tcp_write_space(); those will be cleaned\nup via a dedicated helper in a follow-up net-next series."
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              "value": "AV:L - The vulnerable code runs only in ovpn_tcp_close(), reached via the close() syscall path (inet_release() -\u003e sk_prot-\u003eclose) on a TCP socket attached to the ovpn driver. Remote network packets do not directly invoke this function.\nAC:L - The reproducer is a race between closing the TCP fd and concurrent peer removal (keepalive expiry or OVPN_CMD_DEL_PEER). The attacker controls both sides by timing close() against peer deletion, and can retry until the window is hit.\nPR:N - On an internet-facing OpenVPN server with kernel TCP offload, a remote VPN peer needs no Linux credentials: stopping traffic triggers kernel keepalive expiry and ovpn_socket_release(), while the local daemon concurrently closes the TCP socket as part of normal teardown.\nUI:N - Exploitation does not require any victim user action beyond normal automated VPN server operation reacting to peer timeout or disconnect.\nS:U - Impact is confined to kernel memory corruption and privilege escalation within the host kernel; it does not cross a VM, container, or IOMMU security boundary.\nC:H - This is a use-after-free: after RCU ends, ovpn_tcp_close() re-dereferences sock-\u003epeer on a freed ovpn_socket, enabling reads of attacker-influenced freed heap contents and potential information disclosure.\nI:H - The stale sock-\u003epeer pointer is passed to ovpn_peer_del(), which operates on peer structures and locks; corrupted pointers can cause arbitrary kernel memory corruption exploitable for control-flow hijacking.\nA:H - The UAF can cause kernel oops/panic during peer deletion or TCP close, and use-after-free on kmalloc objects routinely causes system crashes even when not fully weaponized."
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    "dateReserved": "2026-07-19T07:54:57.029Z",
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    "state": "PUBLISHED"
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It then passes sock-\u003epeer\\n(rather than the cached local) to ovpn_peer_del(), re-dereferencing the\\novpn_socket after the RCU read section has ended.\\n\\nUnlike ovpn_tcp_sendmsg(), which uses the same \\\"load under RCU, use\\nafter unlock\\\" pattern but is protected by lock_sock() held across the\\nfunction, ovpn_tcp_close() runs without the socket lock: inet_release()\\ninvokes sk_prot-\u003eclose() without taking lock_sock first.\\n\\novpn_socket_release() can therefore complete its kref_put -\u003e detach -\u003e\\nsynchronize_rcu -\u003e kfree(sock) sequence concurrently, in the window\\nafter ovpn_tcp_close() drops rcu_read_lock() but before it dereferences\\nsock-\u003epeer. The synchronize_rcu() in ovpn_socket_release() protects\\nreaders that use the dereferenced pointer inside the RCU read section,\\nnot those that escape the pointer to a local and use it afterwards.\\n\\nA reproducer follows the pattern of commit 94560267d6c4 (\\\"ovpn: tcp -\\ndon\u0027t deref NULL sk_socket member after tcp_close()\\\"): trigger a peer\\nremoval (keepalive expiration or netlink OVPN_CMD_DEL_PEER) at the same\\nmoment userspace closes the TCP fd. That commit fixed the detach-side\\nof the same race window; this one fixes the close-side at a different\\nvictim.\\n\\nTighten the entry block to read sock-\u003epeer exactly once into the cached\\npeer local, and route all subsequent uses (the hold check, the\\novpn_peer_del() call, and the prot-\u003eclose() invocation) through that\\nlocal. sock-\u003epeer is only ever written once in ovpn_socket_new() under\\nlock_sock(), before rcu_assign_sk_user_data() publishes the ovpn_socket,\\nand is never reassigned afterwards - but the previous multi-read pattern\\nmade that invariant implicit rather than explicit. 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    "redhat_vex": {
      "aggregate_severity": "None",
      "current_release_date": "2026-07-21T09:07:42+00:00",
      "cve": "CVE-2026-64045",
      "id": "CVE-2026-64045",
      "initial_release_date": "2026-07-19T00:00:00+00:00",
      "product_status:known_not_affected": "274",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: ovpn: tcp - use cached peer pointer in ovpn_tcp_close()",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-64045.json",
      "version": "3"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.